The present invention is related to pyrolysis of organic material to produce combustible gas and/or recover chemical components from the pyrolyzed organic material.
Pyrolysis requires the destructive distillation of combustible gases from organic material using heat of combustion of the organic material to maintain the reaction. Organic material to be pyrolyzed is added at the top of a sealed reaction vessel and migrates toward the bottom of the reaction vessel. A grate near the bottom of the reaction vessel supports above it a combustion zone where the residue from the process is combusted to produce the heat required to support the reaction. The heat from the combustion zone is forced upward through the mass of new material by an air blast through the grate. The heated air and gases cause destructive distillation of the carbohydrate material and the generation of carbon monoxide and carbohydrate gases according to the following reaction: EQU C.sub.x H.sub.y O.sub.z +O.sub.2 =C+CO+CO.sub.2 +C.sub.xl-xn H.sub.yl-yn O.sub.zl-zn
In an efficient pyrolysis device in which the desired output is product gas, the free carbon in the products of combustion should be minimized or effectively zero. Further, the CO.sub.2 should also be minimized.
The problem encountered in prior art pyrolysis equipments such as shown in U.S. Pat. No. 3,983,009 is the proper balancing of air flow rate, material agitation and material feed rate to provide the simultaneous reaction parameters which will minimize carbon and carbon dioxide output and maximize product gas output. The primary control in the 3,983,009 patent is a change in the air flow rate through the grate and a change in the rate of addition of new material at the top of the reaction chamber. These parameters must be controlled within very narrow limits and, in practice, it has been discovered that it is not possible to control these parameters on a long-term basis to fully utilize the carbon. An insufficient air flow rate fails to burn the char before it passes through the grate. An excessive air flow rate in the 3,983,009 device expels the unreacted raw material and partially reacted material through the gas outlet.